U.S. patent application number 13/766192 was filed with the patent office on 2013-09-05 for horizontally-oriented gasifier with lateral transfer system.
This patent application is currently assigned to PLASCO ENERGY GROUP INC.. The applicant listed for this patent is PLASCO ENERGY GROUP INC.. Invention is credited to Kenneth Craig Campbell, Mao Pei Cui, Geoffrey Dobbs, Douglas Michael Feasby, Zhiyuan Shen, Andreas Tsangaris.
Application Number | 20130228445 13/766192 |
Document ID | / |
Family ID | 38710680 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130228445 |
Kind Code |
A1 |
Tsangaris; Andreas ; et
al. |
September 5, 2013 |
Horizontally-Oriented Gasifier with Lateral Transfer System
Abstract
A method and apparatus is described for the efficient conversion
of carbonaceous feedstock including municipal solid waste into a
product gas through gasification. More specifically, a
horizontally-oriented gasifier having one or more lateral transfer
system for moving material through the gasifier is provided thereby
allowing for the horizontal expansion of the gasification process
such that there is sequential promotion of feedstock drying,
volatization and char-to-ash conversions.
Inventors: |
Tsangaris; Andreas; (Ottawa,
CA) ; Campbell; Kenneth Craig; (Kitchener, CA)
; Feasby; Douglas Michael; (Sherwood Park, CA) ;
Cui; Mao Pei; (Ottawa, CA) ; Shen; Zhiyuan;
(Ottawa, CA) ; Dobbs; Geoffrey; (Kinburn,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PLASCO ENERGY GROUP INC. |
Kanata |
|
CA |
|
|
Assignee: |
PLASCO ENERGY GROUP INC.
Kanata
CA
|
Family ID: |
38710680 |
Appl. No.: |
13/766192 |
Filed: |
February 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11745427 |
May 7, 2007 |
8435315 |
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13766192 |
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PCT/CA2006/000881 |
Jun 5, 2006 |
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11745427 |
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60798439 |
May 5, 2006 |
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60864116 |
Nov 2, 2006 |
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60911179 |
Apr 11, 2007 |
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60797973 |
May 5, 2006 |
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Current U.S.
Class: |
201/32 |
Current CPC
Class: |
C10J 2300/1671 20130101;
Y02E 20/12 20130101; C10J 2300/0946 20130101; C10J 3/482 20130101;
C10J 2200/154 20130101; C10J 2200/158 20130101; C10J 2300/1693
20130101; C10J 3/002 20130101; C10J 2200/09 20130101; C10J
2300/0956 20130101; C10J 2200/15 20130101; C10J 2300/0976 20130101;
C10J 2300/093 20130101; C10J 2300/1603 20130101; C10J 3/48
20130101; C10B 7/06 20130101 |
Class at
Publication: |
201/32 |
International
Class: |
C10B 7/06 20060101
C10B007/06 |
Claims
1-9. (canceled)
10. A method for converting a carbonaceous feedstock to an off-gas
and ash, comprising the steps of: a) establishing three regional
temperature zones in a gasifier; wherein a first zone has a
temperature which promotes drying, a second zone has a temperature
which promotes volatization and a third zone has a temperature
which promotes char-to-ash conversion; b) providing carbonaceous
feedstock to the first zone and maintaining the carbonaceous
feedstock at the first zone for a period of time to obtain a
substantially dried reactant material; c) passing the substantially
dried reactant material to the second zone for a period of time
such that volatile components of the substantially dried reactant
material are volatilized to form off-gas; and d) passing residual
char from the second zone to the third zone for period of time such
that the char is converted to additionally off-gas and ash.
11. The method of claim 10, wherein movement of reactant material
through the gasifier is controlled based on pile height or pile
profile.
12. The method of claim 10, comprising inputting process additives
into the gasifier.
13. The method of claim 10, wherein the method is subject to
feedback control.
14. The method of claim 12, wherein the method is subject to
feedback control.
15. The method of claim 10, further comprising the step of
converting the ash to slag.
16. The method of claim 10, wherein the gasifier is a horizontally
oriented gasifier.
17. The method of claim 10, further comprising reformulating the
off-gas.
18. The method of claim 17, wherein reformulating the off-gas
comprises treating the off-gas with plasma heat.
19. The method of claim 10, further comprising treating the off-gas
with a cyclonic oxidizer.
20. The method of claim 10, wherein the carbonaceous feedstock is
municipal solid waste.
21. The method of claim 12, wherein the process additives are hot
air and/or steam.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of priority under 35 U.S.C.
.sctn.119(e) from U.S. Provisional Application Ser. No. 60/798,439,
filed May 5, 2006. This application also claims benefit of priority
to International Patent Application No. PCT/CA2006/000881, filed
Jun. 5, 2006. This application also claims benefit of priority
under 35 U.S.C. .sctn.119(e) from U.S. Provisional Application Ser.
No. 60/864,116, filed Nov. 2, 2006. This application also claims
benefit of priority under 35 U.S.C. .sctn.119(e) from U.S.
Provisional Application Ser. No. 60/911,179, filed Apr. 11, 2007.
This application also claims benefit of priority under 35 U.S.C.
.sctn.119(e) from U.S. Provisional Application Ser. No. 60/797,973,
filed May 5, 2006. The contents of all of the aforementioned
applications are hereby expressly incorporated by reference in
their entirety and for all purposes.
FIELD OF THE INVENTION
[0002] This invention pertains to the field of carbonaceous
feedstock gasification and in particular, to a
horizontally-oriented gasifier with a lateral transfer system.
BACKGROUND OF THE INVENTION
[0003] Gasification is a process that enables the conversion of
carbonaceous feedstock, such as municipal solid waste (MSW) or
coal, into a combustible gas. The gas can be used to generate
electricity, steam or as a basic raw material to produce chemicals
and liquid fuels.
[0004] Possible uses for the gas include: the combustion in a
boiler for the production of steam for internal processing and/or
other external purposes, or for the generation of electricity
through a steam turbine; the combustion directly in a gas turbine
or a gas engine for the production of electricity; fuel cells; the
production of methanol and other liquid fuels; as a further
feedstock for the production of chemicals such as plastics and
fertilizers; the extraction of both hydrogen and carbon monoxide as
discrete industrial fuel gases; and other industrial
applications.
[0005] Generally, the gasification process consists of feeding
carbonaceous feedstock into a heated chamber (the gasifier) along
with a controlled and/or limited amount of oxygen and optionally
steam. In contrast to incineration or combustion, which operate
with excess oxygen to produce CO.sub.2, H.sub.2O, SO.sub.x, and
NOx, gasification processes produce a raw gas composition
comprising CO, H.sub.2, H.sub.2S, and NH.sub.3. After clean-up, the
primary gasification products of interest are H.sub.2 and CO.
[0006] Useful feedstock can include any municipal waste, waste
produced by industrial activity and biomedical waste, sewage,
sludge, coal, heavy oils, petroleum coke, heavy refinery residuals,
refinery wastes, hydrocarbon contaminated soils, biomass, and
agricultural wastes, tires, and other hazardous waste. Depending on
the origin of the feedstock, the volatiles may include H.sub.2O,
H.sub.2, N.sub.2, O.sub.2, CO.sub.2, CO, CH.sub.4, H.sub.2S,
NH.sub.3, C.sub.2H.sub.6, unsaturated hydrocarbons such as
acetylenes, olefins, aromatics, tars, hydrocarbon liquids (oils)
and char (carbon black and ash).
[0007] As the feedstock is heated, water is the first constituent
to evolve. As the temperature of the dry feedstock increases,
pyrolysis takes place. During pyrolysis the feedstock is thermally
decomposed to release tars, phenols, and light volatile hydrocarbon
gases while the feedstock is converted to char.
[0008] Char comprises the residual solids consisting of organic and
inorganic materials. After pyrolysis, the char has a higher
concentration of carbon than the dry feedstock and may serve as a
source of activated carbon. In gasifiers operating at a high
temperature (>1,200.degree. C.) or in systems with a high
temperature zone, inorganic mineral matter is fused or vitrified to
form a molten glass-like substance called slag.
[0009] Since the slag is in a fused, vitrified state, it is usually
found to be non-hazardous and may be disposed of in a landfill as a
non-hazardous material, or sold as an ore, road-bed, or other
construction material. It is becoming less desirable to dispose of
waste material by incineration because of the extreme waste of fuel
in the heating process and the further waste of disposing, as a
residual waste, material that can be converted into a useful syngas
and solid material.
[0010] The means of accomplishing a gasification process vary in
many ways, but rely on four key engineering factors: the atmosphere
(level of oxygen or air or steam content) in the gasifier; the
design of the gasifier; the internal and external heating means;
and the operating temperature for the process. Factors that affect
the quality of the product gas include: feedstock composition,
preparation and particle size; gasifier heating rate; residence
time; the plant configuration including whether it employs a dry or
slurry feed system, the feedstock-reactant flow geometry, the
design of the dry ash or slag mineral removal system; whether it
uses a direct or indirect heat generation and transfer method; and
the syngas cleanup system. Gasification is usually carried out at a
temperature in the range of about 650.degree. C. to 1200.degree.
C., either under vacuum, at atmospheric pressure or at pressures up
to about 100 atmospheres.
[0011] There are a number of systems that have been proposed for
capturing heat produced by the gasification process and utilizing
such heat to generate electricity, generally known as combined
cycle systems.
[0012] The energy in the product gas coupled with substantial
amounts of recoverable sensible heat produced by the process and
throughout the gasification system can generally produce sufficient
electricity to drive the process, thereby alleviating the expense
of local electricity consumption. The amount of electrical power
that is required to gasify a ton of a carbonaceous feedstock
depends directly upon the chemical composition of the
feedstock.
[0013] If the gas generated in the gasification process comprises a
wide variety of volatiles, such as the kind of gas that tends to be
generated in a low temperature gasifier with a "low quality"
carbonaceous feedstock, it is generally referred to as off-gas. If
the characteristics of the feedstock and the conditions in the
gasifier generate a gas in which CO and H.sub.2 are the predominant
chemical species, the gas is referred to as syngas. Some
gasification facilities employ technologies to convert the raw
off-gas or the raw syngas to a more refined gas composition prior
to cooling and cleaning through a gas quality conditioning
system.
[0014] Utilizing plasma heating technology to gasify a material is
a technology that has been used commercially for many years. Plasma
is a high temperature luminous gas that is at least partially
ionized, and is made up of gas atoms, gas ions, and electrons.
Plasma can be produced with any gas in this manner. This gives
excellent control over chemical reactions in the plasma as the gas
might be neutral (for example, argon, helium, neon), reductive (for
example, hydrogen, methane, ammonia, carbon monoxide), or oxidative
(for example, oxygen, carbon dioxide). In the bulk phase, a plasma
is electrically neutral.
[0015] Some gasification systems employ plasma heat to drive the
gasification process at a high temperature and/or to refine the
offgas/syngas by converting, reconstituting, or reforming longer
chain volatiles and tars into smaller molecules with or without the
addition of other inputs or reactants when gaseous molecules come
into contact with the plasma heat, they will disassociate into
their constituent atoms. Many of these atoms will react with other
input molecules to form new molecules, while others may recombine
with like atoms. As the temperature of the molecules in contact
with the plasma heat decreases all atoms fully recombine. As input
gases can be controlled stoichiometrically, output gases can be
controlled to, for example, produce substantial levels of carbon
monoxide and insubstantial levels of carbon dioxide.
[0016] The very high temperatures (3000 to 7000.degree. C.)
achievable with plasma heating enable a high temperature
gasification process where virtually any input feedstock including
waste in as-received condition, including liquids, gases, and
solids in any form or combination can be accommodated. The plasma
technology can be positioned within a primary gasification chamber
to make all the reactions happen simultaneously (high temperature
gasification), can be positioned within the system to make them
happen sequentially (low temperature gasification with high
temperature refinement), or some combination thereof.
[0017] The gas produced during the gasification of carbonaceous
feedstock is usually very hot but may contain small amounts of
unwanted compounds and requires further treatment to convert it
into a useable product. Once a carbonaceous material is converted
to a gaseous state, undesirable substances such as metals, sulfur
compounds and ash may be removed from the gas. For example, dry
filtration systems and wet scrubbers are often used to remove
particulate matter and acid gases from the gas produced during
gasification. A number of gasification systems have been developed
which include systems to treat the gas produced during the
gasification process.
[0018] These factors have been taken into account in the design of
various different systems which are described, for example, in U.S.
Pat. Nos. 6,686,556, 6,630,113, 6,380,507; 6,215,678, 5,666,891,
5,798,497, 5,756,957, and U.S. Patent Application Nos.
2004/0251241, 2002/0144981. There are also a number of patents
relating to different technologies for the gasification of coal for
the production of synthesis gases for use in various applications,
including U.S. Pat. Nos. 4,141,694; 4,181,504; 4,208,191;
4,410,336; 4,472,172; 4,606,799; 5,331,906; 5,486,269, and
6,200,430.
[0019] Prior systems and processes have not adequately addressed
the problems that must be dealt with on a continuously changing
basis. Some of these types of gasification systems describe means
for adjusting the process of generating a useful gas from the
gasification reaction. Accordingly, it would be a significant
advancement in the art to provide a system that can efficiently
gasify carbonaceous feedstock in a manner that maximizes the
overall efficiency of the process, and/or the steps comprising the
overall process.
SUMMARY OF THE INVENTION
[0020] An object of the present invention is to provide a
horizontally-oriented gasifier with lateral transfer system. In
accordance with an aspect of the invention, there is provided a
horizontally-oriented gasifier comprising a horizontally-oriented
gasification chamber having one or more feedstock inputs, one or
more gas outlets and a solid residue outlets; a chamber heating
system; one or more lateral transfer units for moving material
through the gasifier during processing; and a control system for
controlling movement of the one or more lateral transfer units.
[0021] In accordance with another aspect of the invention, there is
provided a process for converting a feedstock to an off-gas and
ash, comprising the steps of: [0022] a) establishing three regional
temperature zones in an horizontally-oriented gasifier; wherein a
first zone has a temperature which promotes drying, a second zone
has a temperature which promotes volatization and a third zone has
a temperature which promotes char-to-ash conversion; [0023] b)
providing carbonaceous feedstock to the first zone and maintaining
the carbonaceous feedstock at the first zone for a period of time
to obtain a substantially dried reactant material; [0024] c)
passing the substantially dried reactant material to the second
zone for a period of time such that volatile components of the
dried reactant material are volatilized to form off-gas; [0025] d)
passing residual char from the second zone to the third zone for
period of time such that the char is converted to additionally
off-gas and ash.
[0026] This invention provides a horizontally-oriented gasifier
with lateral transfer system that enables extraction of volatiles
throughout the various stages of gasification of carbonaceous
feedstock to be optimized. Feedstock is introduced at one end of
the gasifier and is moved through the gasifier during processing by
one or more lateral transfer units. The temperature at the top of
the material pile generally increases as gasification proceeds
through drying, volatilization and char-to-ash conversion (carbon
conversion) with the simultaneous production of CO and CO.sub.2. A
control system obtains information from measurable parameters such
as temperature and pile height or profile and manages the movement
of each lateral transfer unit independently.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Embodiments of the invention will now be described, by way
of example only, by reference to the attached Figures, wherein:
[0028] FIG. 1 is a schematic of a horizontally-oriented stepped
floor gasifier of the invention, detailing the feedstock input, gas
outlet, ash outlet and lateral transfer system.
[0029] FIG. 2 is a flow diagram showing the different regions of
the gasifier in general terms.
[0030] FIG. 3 is a representation of the gasification processes
occurring in Regions 1, 2 and 3 of one embodiment of the
gasifier.
[0031] FIG. 4 is a cross-sectional view through one embodiment of
the gasifier, detailing the feedstock input, gas outlet, ash
outlet, lateral transfer system, additive ports and access
ports.
[0032] FIG. 5 is a central longitudinal cross-sectional view
through the embodiment of the gasifier illustrated in FIG. 4,
detailing the thermocouples and process additive ports.
[0033] FIG. 6 is a perspective view of the embodiment of the
gasifier illustrated in FIGS. 4 and 5.
[0034] FIG. 7 illustrates a view of the outside of the embodiment
of the gasifier illustrated in FIGS. 4 to 6 detailing the external
elements of the lateral transfer system.
[0035] FIG. 8 illustrates a portion of a lateral transfer unit of
the gasifier illustrated in FIGS. 4 to 6.
[0036] FIG. 9 illustrates a bottom view of the lateral transfer
unit illustrated in FIG. 8.
[0037] FIG. 10 illustrates an alternative embodiment of the lateral
transfer unit illustrated in FIG. 8.
[0038] FIG. 11 is a perspective view of one embodiment of the
gasifier, detailing the feedstock input, gas outlet, ash outlet,
ram enclosure and access ports.
[0039] FIG. 12 is a side view of the gasifier illustrated in FIG.
11 detailing the air boxes, ash can and dust collector.
[0040] FIG. 13 is a central longitudinal cross-sectional view
through the gasifier illustrated in FIGS. 11 and 12, detailing the
feedstock input, gas outlet, ash outlet, lateral transfer system,
thermocouples and access ports.
[0041] FIG. 14 illustrates a cross sectional view of the gasifier
of FIGS. 11 to 13 detailing the air boxes, ram fingers and ash
extractor screw.
[0042] FIG. 15 illustrates a close-up cross sectional view of FIG.
14 detailing the air boxes, ram fingers, ash extractor screw and
serrated edge of step C.
[0043] FIG. 16 is a sectional view of the gasifier of FIGS. 11 to
12 detailing the refractory.
[0044] FIG. 17 details the air box assembly of Step A and B of the
gasifier illustrated in FIGS. 11 to 16.
[0045] FIG. 18 illustrates a cross sectional view of the Step C air
box of the gasifier illustrated in FIGS. 11 to 16.
[0046] FIG. 19 illustrates a side view of the outside of the
gasifier of FIGS. 11 to 16 detailing the Step C air box and ash
screw extrator.
[0047] FIG. 20 illustrates a cross sectional view of the gasifier
of FIGS. 11 to 16 detailing an air box.
[0048] FIG. 21 illustrates a cross sectional view of the gasifier
of FIGS. 11 to 16 detailing the sealing of the upstream edge of the
air box with a resilient sheet sealing between the carrier ram and
the air box top plate.
[0049] FIG. 22 details the dust seal of the multiple-finger carrier
ram of the gasifier illustrated in FIGS. 11 to 16.
[0050] FIG. 23 showing the dust removal system of one embodiment of
the gasifier illustrated in FIGS. 11 to 16 detailing the dust
pusher, dust can attachment, shutter, operator handle and chain
mechanism.
[0051] FIG. 24 details the ram enclosure of the gasifier
illustrated in FIGS. 11 to 16 detailing a portion the lateral
transfer unit structure.
[0052] FIG. 25 details the multiple-finger carrier ram setup at
Step 1 of the gasifier illustrated in FIGS. 11 to 16.
[0053] FIG. 26 is an illustration detailing the level switch
locations in one embodiment of the invention.
[0054] FIG. 27 is an illustration detailing two reactant material
pile profiles for the gasifier of Example 2, according to an
embodiment of the invention.
[0055] FIG. 28 is an illustration of the thermocouple for an
embodiment of the invention, detailing the deflector.
[0056] FIG. 29 is an illustration of the gasifier of Example 2
coupled to a gas reformulating chamber.
[0057] FIG. 30 is an alternative view of the gasifier of Example 2
coupled to a gas reformulating chamber.
[0058] FIG. 31 is a cross sectional view of the gasifier of Example
2 coupled to a gas reformulating chamber detailing one plasma
torch.
[0059] FIG. 32 is schematic showing the converter of FIGS. 29 to 31
incorporated into power plant.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0060] As used herein, the term "sensing element" is defined to
describe any element of the system configured to sense a
characteristic of a process, a process device, a process input or
process output, wherein such characteristic may be represented by a
characteristic value useable in monitoring, regulating and/or
controlling one or more local, regional and/or global processes of
the system. Sensing elements considered within the context of a
gasification system may include, but are not limited to, sensors,
detectors, monitors, analyzers or any combination thereof for the
sensing of process, fluid and/or material temperature, pressure,
flow, composition and/or other such characteristics, as well as
material position and/or disposition at any given point within the
system and any operating characteristic of any process device used
within the system. It will be appreciated by the person of ordinary
skill in the art that the above examples of sensing elements,
though each relevant within the context of a gasification system,
may not be specifically relevant within the context of the present
disclosure, and as such, elements identified herein as sensing
elements should not be limited and/or inappropriately construed in
light of these examples.
[0061] As used herein, the term "response element" is defined to
describe any element of the system configured to respond to a
sensed characteristic in order to operate a process device
operatively associated therewith in accordance with one or more
pre-determined, computed, fixed and/or adjustable control
parameters, wherein the one or more control parameters are defined
to provide a desired process result. Response elements considered
within the context of a gasification system may include, but are
not limited to static, pre-set and/or dynamically variable drivers,
power sources, and any other element configurable to impart an
action, which may be mechanical, electrical, magnetic, pneumatic,
hydraulic or a combination thereof, to a device based on one or
more control parameters. Process devices considered within the
context of a gasification system, and to which one or more response
elements may be operatively coupled, may include, but are not
limited to, material and/or feedstrock input means, heat sources
such as plasma heat sources, additive input means, various gas
blowers and/or other such gas circulation devices, various gas flow
and/or pressure regulators, and other process devices operable to
affect any local, regional and/or global process within a
gasification system. It will be appreciated by the person of
ordinary skill in the art that the above examples of response
elements, though each relevant within the context of a gasification
system, may not be specifically relevant within the context of the
present disclosure, and as such, elements identified herein as
response elements should not be limited and/or inappropriately
construed in light of these examples.
[0062] As used herein, the term, "reactant material" can mean
feedstock, including but not limited to partially or fully
processed feedstock.
[0063] As used herein, the term "(carbonaceous) feedstock" can be
any carbonaceous material appropriate for gasifying in the present
gasification process, and can include, but is not limited to, any
waste materials, coal (including low grade, high sulfur coal not
suitable for use in coal-fired power generators), petroleum coke,
heavy oils, biomass, sewage sludge, sludge from pulp and paper
mills and agricultural wastes. Waste materials suitable for
gasification include both hazardous and non-hazardous wastes, such
as municipal waste, wastes produced by industrial activity (paint
sludges, off-spec paint products, spent sorbents), automobile
fluff, used tires and biomedical wastes, any carbonaceous material
inappropriate for recycling, including non-recyclable plastics,
sewage sludge, coal, heavy oils, petroleum coke, heavy refinery
residuals, refinery wastes, hydrocarbon contaminated solid waste
and biomass, agricultural wastes, tires, hazardous waste,
industrial waste and biomass. Examples of biomass useful for
gasification include, but are not limited to, waste or fresh wood,
remains from fruit, vegetable and grain processing, paper mill
residues, straw, grass, and manure.
[0064] As used herein, the term, "input" denotes that which is
about to enter or be communicated to any system or component
thereof, is currently entering or being communicated to any system
or component thereof, or has previously entered or been
communicated to any system or component thereof. An input includes,
but is not limited to, compositions of matter, information, data,
and signals, or any combination thereof. In respect of a
composition of matter, an input may include, but is not limited to,
influent(s), reactant(s), reagent(s), fuel(s), object(s) or any
combinations thereof. In respect of information, an input may
include, but is not limited to, specifications and operating
parameters of a system. In respect of data, an input may include,
but is not limited to, result(s), measurement(s), observation(s),
description(s), statistic(s), or any combination thereof generated
or collected from a system. In respect of a signal, an input may
include, but is not limited to, pneumatic, electrical, audio, light
(visual and non-visual), mechanical or any combination thereof. An
input may be defined in terms of the system, or component thereof,
to which it is about to enter or be communicated to, is currently
entering or being communicated to, or has previously entered or
been communicated to, such that an input for a given system or
component of a system may also be an Output in respect of another
system or component of a system. Input can also denote the action
or process of entering or communicating with a system.
[0065] As used herein, the term "output" denotes that which is
about to exit or be communicated from any system or component
thereof, is currently exiting or being communicated from any system
or component thereof, or has previously exited or been communicated
from any system or component thereof. An output includes, but is
not limited to, compositions of matter, information, data, and
signals, or any combination thereof. In respect of a composition of
matter, an output may include, but is not limited to, effluent(s),
reaction product(s), process waste(s), fuel(s), object(s) or any
combinations thereof. In respect of information, an output may
include, but is not limited to, specifications and operating
parameters of a system. In respect of data, an output may include,
but is not limited to, result(s), measurement(s), observation(s),
description(s), statistic(s), or any combination thereof generated
or collected from a system. In respect of a signal, an output may
include, but is not limited to, pneumatic, electrical, audio, light
(visual and non-visual), mechanical or any combination thereof. An
output may be defined in terms of the system, or component thereof,
to which it is about to exit or be communicated from, currently
exiting or being communicated from, or has previously exited or
been communicated from, such that an output for a given system or
component of a system may also be an input in respect of another
system or component of a system. Output can also denote the action
or process of exiting or communicating with a system.
Overview of the System
[0066] Referring to FIG. 1, this invention provides a
horizontally-oriented gasifier (2000) having one or more feedstock
input(s) (2004), one or more gas outlet(s) (2006) and a solid
residue (ash) outlet (2008). Material enters the gasifier (2000)
via the one or more feedstock input(s) (2004) and is moved through
the gasifier (2000) during processing by one or more lateral
transfer units (2010) which is controlled by a control system.
[0067] The invention provides a horizontally-oriented gasifier
(2000) comprising a lateral transfer system to facilitate the
extraction of gaseous molecules from carbonaceous feedstock. In
particular, the invention provides a gasifier in which the
gasification process is facilitated by sequentially promoting
drying, volatilization and char-to-ash conversion (carbon
conversion). This is accomplished by allowing drying to occur at a
certain temperature range prior to moving the material to another
region and allowing volatilization to occur at another temperature
range, prior to moving the material to another region and allowing
char-to-ash conversion to occur at another temperature range.
Accordingly, as the material in the gasifier is moved from the feed
area towards the solid residue end by one or more lateral transfer
units (2010) it goes through different degrees of drying,
volatization and char-to-ash conversion (carbon conversion).
[0068] To facilitate movement of reactant material, the individual
lateral transfer units (2010) can be controlled independently or a
group of two or more lateral transfer units (2010) can be
controlled in a coordinated manner.
[0069] Thus, each area in the horizontally-oriented gasifier
experiences temperature ranges and optional process additives
(2019) (such as air, oxygen and/or steam) that promote a certain
stage of the gasification process. In a pile of reactant material,
all stages of gasification are occurring concurrently, however
individual stages are favored at a certain temperature range.
[0070] By physically moving the material through the gasifier, the
gasification process can be facilitated by allowing as much drying
as energetically efficient to occur prior to raising the
temperature of the material to promote volatilization. The process
then seeks to allow as much volatilization as energetically
efficient to occur prior to raising the temperature of the material
to promote char-to-ash conversion (carbon conversion).
[0071] As illustrated in FIGS. 2 and 3, the horizontal expansion of
the gasification process achieved by use of the invention
facilitates the gasification process by regionally promoting one or
more of the stages (drying, volatization and char-to-ash
conversion) of the gasification process in response to the
characteristics of the reactant material at that particular
location in the gasifier.
[0072] Theoretically, the conditions in the gasifier at any
location could be optimized in response to the character of the
reactant material at that particular location. A practical
embodiment of this concept, however, is to segregate the gasifier
into a finite number of regions optimized in response to the
general or average reactant material characteristics of a larger
area. For example, the gasifier could therefore be segregated into
two, three, four or more regions depending on the characteristics
of the feedstock. To facilitate understanding, the discussion below
describes segregating the gasifier into three regions. The
invention, however, is not limited to a gasifier having three
regions.
[0073] Although as discussed above the processes of gasification
are occurring in a continuous and concurrent manner throughout the
gasifier, the gasifier can be notionally divided into regions. In
the three region embodiment:
Region I: Promotes Drying of the Material
[0074] Referring to FIG. 2, Region I would be the area between
lines 310 and 320. Feedstock is delivered into the gasifier at
Region I. The normal temperature range for this region (as measured
at the bottom of the material pile) lies between about 300 and
900.degree. C. The major process here is that of drying which
occurs predominantly at the top and in middle of the pile of
material and at a temperature above about 100.degree. C. In
addition, some volatilization and some char-to-ash conversion
(carbon conversion) occurs in this region.
Region II: Promotes Volatilization of the Material
[0075] Referring to FIG. 3, Region II would be the region between
lines 320 and 330. The material pile has a bottom temperature range
between about 400 and 950.degree. C. The main process occurring in
Region II is that of volatilization with the remainder of the
drying operation as well as a substantial amount of char to ash
conversion (carbon conversion).
Region III: Char-to-Ash Conversion (Carbon Conversion)
[0076] Referring to FIG. 3, Region III would be the region between
lines 330 and 340. The Region III temperature range lies between
about 500 and 1000.degree. C. Although, in one embodiment in order
to avoid agglomeration of the ash, the maximum temperature in this
region does not exceed about 950.degree. C. The major process in
Region III is that of carbon conversion with a lesser amount (the
remainder) of volatilization. By this time the moisture from the
reactant material has been removed. By the end of this region, the
majority of the solid residue is ash.
[0077] In one embodiment, the ash from Region III is translocated
into an ash collection chamber. Appropriate ash collection chambers
are known in the art and accordingly, a worker skilled in the art
having regard to the requirements of the system would readily know
the size, shape and manufacture of an appropriate ash collection
chamber.
[0078] In one embodiment, the ash will be translocated into a water
tank for cooling, from which the gasifier residue is transmitted
through a conduit, optionally, under control of a valve, to a point
of discharge.
[0079] In one embodiment, the ash is translocated into a solid
residue conditioning conversion chamber for the conversion of
ash-to-slag.
Horizontally-Oriented Gasifier
[0080] Referring now to FIG. 1, the gasifier (2000) comprises a
horizontally-oriented gasification chamber (2002) having a
feedstock input (2004), gas outlet (2006) and ash (solid residue)
outlet (2008). The gasifier further comprises a lateral transfer
system having one or more lateral transfer units (2010) for
transporting solid material through the gasification chamber.
[0081] In one embodiment, the number of lateral transfer units in a
particular gasifier is dependent on the path length reactant
material must travel and the distance reactant material can be
moved by each lateral transfer unit and is a compromise between
minimizing the magnitude of process disturbances caused by each
discrete transfer and mechanical complexity, cost, and
reliability.
[0082] During processing, feedstock is introduced into the chamber
(2002) at one end; hereafter referred to as the feed end, through
the feedstock input (2004) and is transported from the feed end
through the various regions in the gasification chamber towards the
ash (solid residue) outlet (2008) or ash end. As the feed material
progresses through the chamber, it loses its mass and volume as its
volatile fraction is volatilized to form off-gas and the resulting
char is reacted to form additional off-gas and ash.
[0083] Due to this progressive conversion, the height of the
material (pile height) decreases from the feed end to the ash end
of the chamber and levels off when only solid residue (ash)
remains.
[0084] In one embodiment, the off-gas escapes through the gas
outlet (2006) into, for example, a gas refinement chamber where it
can undergo further processing including plasma heat-dependent
processing or into a storage chamber or tank. The solid residue
(ash) is transported through the ash outlet (2008) to, for example,
an ash collection chamber or a solid residue conditioning chamber
for further processing.
[0085] In one embodiment, the gasifier has a stepped floor having a
plurality of floor levels or steps. Optionally, each floor level is
sloped. In one embodiment the floor level is sloped between about 5
and about 10 degrees.
[0086] In one embodiment of the step-floor gasifier, the individual
steps (floor levels) correlate, at least in part, with the
individual regions discussed above, with each region or step having
conditions optimized for different degrees of drying,
volatilization and carbon conversion. For convenience, the
uppermost step will be referred to as step A; the next step will be
referred to as step B, etc. Corresponding lateral transfer units
will be identified with the same letter, i.e. lateral transfer unit
A or ram A services step A, lateral transfer unit B or ram B
services step B.
[0087] In the three step embodiment, there is an upper step or step
A (2012), middle step or step B (2014) and a lower step or step C
(2016).
[0088] The feedstock is fed onto the upper step (step A) (2012).
The normal temperature range for this step (as measured at the
bottom of the material pile) lies between 300 and 900.degree.
C.
[0089] Step B is designed to have a bottom temperature range
between 400 and 950.degree. C. to promote volatilization with the
remainder of the drying operation as well as a substantial amount
of char-to-ash conversion (carbon conversion).
[0090] Step C temperature range lies between 500 and 1000.degree.
C. The major process in Step C is that of char-to-ash conversion
(carbon conversion) with a lesser amount (the remainder) of
volatilization.
[0091] In one embodiment, movement over the steps is facilitated by
the lateral transfer system with each step optionally being
serviced by an independently controlled lateral transfer unit.
Design Considerations for the Chamber
[0092] The chamber of a gasifier is designed to provide a sealed,
insulated space for processing of the feedstock into off-gas and to
allow for passage of off-gas to downstream process such as cooling
or refining or other and optionally for removal of ash for
subsequent further processing. Such processing of the feedstock is
facilitated by a design that promotes the introduction of process
additives, such as hot air and/or steam, into the reactant material
throughout the gasifier and enables control of the pile height of
the reactant material and its movement through the gasifier without
disruption or bridging. The design may optionally provide for
access to the interior of the gasifier for inspection, maintenance
and repair.
[0093] A gasifier is designed to accomplish extraction of volatile
compounds from the carbonaceous feedstock. Thus, factors such as
heat transfer, gas flow, mixing of process additives, among others,
can be taken into account when designing the shape of the gasifier.
The use of computer modeling can facilitate the optimization of
gasifier design. Appropriate computer modeling systems and
simulators are known in the art and include the Chemical Process
Simulator as detailed in U.S. Pat. No. 6,817,388 (incorporated by
reference).
[0094] In one embodiment, in addition to using the Chemical Process
Simulator, flow modeling of the gasifier can be performed to ensure
proper mixing of process inputs, and to ensure that kinetic effects
are not significant.
[0095] The physical design characteristics of the gasifier are
determined by a number of factors. These factors include, for
example, the chemical composition and physical characteristics of
the feedstock to be processed including moisture content, particle
size, hardness and flow characteristics; system throughput;
required conversion efficiency (residence time); desired gasifier
geometry (l/d ratio); material transport characteristics; mixing
characteristics (solid and gas); gas superficial velocity and
additive distribution among others. The internal configuration and
size of the gasification chamber are dictated, in part, by the
operational characteristics through analyses of the input waste
stream to be processed.
[0096] As discussed above, the feedstock is introduced into the
gasifier via the feedstock input (2004) and moves through the
gasification chamber during processing. This movement is achieved,
wholly or in part, by the use of a lateral transfer system.
[0097] In one embodiment, to facilitate reactant material transfer,
when designing the gasifier the dynamics of reactant material
transfer through the gasifier can be considered such that the risk
of bridging, obstruction of reactant material flow by various
instrumentations or by resistance from downstream reactant material
or by wall friction can be reduced or eliminated.
[0098] During processing, air as a source of oxygen is introduced
into the chamber. Optionally, the method of injecting air can be
selected to facilitate an even flow of air into the gasification
chamber, prevent hot spot formation and/or improve temperature
control. The air can be introduced through the sides of the
chamber, optionally from near the bottom of the chamber, or can be
introduced through the floor of the chamber, or through both.
[0099] Also to be considered in the design of the gasifier is the
position, orientation and number of the process additive inputs.
The process additives can optionally be injected into the gasifier
at locations where they will ensure most efficient reaction to
achieve the desired conversion result.
[0100] In one embodiment, the floor of the gasification chamber is
perforated to varying degrees to allow for introduction of process
additives, such as air at the base of the material pile.
[0101] In one embodiment, the side-walls of the chamber slope
inwards towards the bottom to achieve a small enough width for good
air penetration from the sides while still having the required
volume of material. The slope angle can optionally be made steep
enough to assure that the material will drop towards the bottom of
the chamber during processing.
[0102] In one embodiment, the gasification chamber is a steel
weldment with connection features for feedstock input, air and
steam input, gas output and ash removal.
[0103] In one embodiment, the gasification chamber is tubular.
[0104] In one embodiment, the roof or upper portion of the
gasification chamber is designed to optimize flow and residence
time of gas throughout the gasification chamber. The roof portion
can be flat, domed, half-cylindrical or another practical
configuration that promotes the flow of gas through the
gasification chamber.
[0105] In one embodiment, the gasification chamber of the invention
is a horizontal vessel with its cross-section optionally including
a semi-circular dome or arched roof and optionally with a tapered
lower section.
Materials
[0106] The gasification chamber is a partially or fully
refractory-lined chamber with an internal volume sized to
accommodate the appropriate amount of material for the required
solids residence time. The refractory protects the gasification
chamber from the high temperature and corrosive gases and minimizes
unnecessary loss of heat from the process. The refractory material
can be a conventional refractory material well-known to those
skilled in the art and which is suitable for use for a high
temperature e.g. up to about 1100.degree. C., un-pressurized
reaction. When choosing a refractory system factors to be
considered include internal temperature, abrasion; erosion and
corrosion; desired heat conservation/limitation of temperature of
the external vessel; desired life of the refractory. Examples of
appropriate refractory material include high temperature fired
ceramics, i.e., aluminum oxide, aluminum nitride, aluminum silicate
boron nitride, zirconium phosphate, glass ceramics and high alumina
brick containing principally, silica, alumina, chromia and titania.
To further protect the gasification chamber from corrosive gases
the chamber is, optionally, partially or fully lined with a
protective membrane. Such membranes are known in the art and, as
such, a worker skilled in the art would readily be able to identify
appropriate membranes based on the requirements of the system and,
for example, include Sauereisen High Temperature Membrane No
49.
[0107] In one embodiment, the refractory is a multilayer design
with a high density layer on the inside to resist the high
temperature, abrasion, erosion and corrosion. Outside the high
density material is a lower density material with lower resistance
properties but higher insulation factor. Optionally, outside this
layer is a very low density foam board material with very high
insulation factor and can be used because it will not be exposed to
abrasion of erosion. Appropriate materials for use in a multilayer
refractory are well known in the art.
[0108] In one embodiment, the multilayer refractory comprises an
internally oriented chromia layer; a middle alumina layer and an
outer insboard layer.
[0109] The wall of the chamber can optionally incorporate supports
for the refractory lining or refractory anchors. Appropriate
refractory supports and anchors are known in the art.
Lateral Transfer System
Design Objectives
[0110] Material is moved through the gasification chamber in order
to promote specific stages of the gasification process (drying,
volatilization, char-to-ash conversion). To facilitate control of
the gasification process, material movement through the
gasification chamber can be varied (variable movement) depending on
process requirements. This lateral movement of material through the
gasifier is achieved via the use of a lateral transfer system
comprising one or more lateral transfer units. Movement of reactant
material by the lateral transfer system can be optimized by varying
the movement speed, the distance a lateral transfer unit moves and
the when multiple lateral transfer units are used, the sequence in
which the plurality of lateral transfer units are moved in relation
to each other. The one or more lateral transfer units can act in a
coordinated manner or individual lateral transfer units can act
independently. In order to facilitate control of the material flow
rate and pile height the individual lateral transfer units can be
moved individually, at varying speeds, at varying movement
distances, at varying frequency of movement.
[0111] By strictly regulating the movement of the one or more
lateral transfer units, the reactant pile can obtain the desired
profile such that both wall friction and back pressure imposed by
reactant material sitting on downstream stages is reduced or
eliminated.
[0112] The lateral transfer system must be able to effectively
operate in the harsh conditions of the gasifier and in particular
must be able to operate at high temperatures. Moreover, the high
temperature environment and abrasive nature of the feedstock
demands that the lateral transfer system be robust.
[0113] In embodiments in which the hot air is supplied through the
floor of the gasifier, the lateral transfer design can be a
compromise between assurance of motion versus degradation of
processing by blocking air-flow.
Lateral Transfer Units
[0114] The individual lateral transfer units comprise a moving
element and a guiding element or alignment element. It would be
apparent to a worker skilled in the art that the moving element can
be equipped with appropriate guide engagement elements.
[0115] The moving element can include, but is not limited to, a
shelf/platform, pusher ram or carrier rams, plow, screw element,
conveyor or a belt. The rams can include a single ram or
multiple-finger ram.
[0116] In one embodiment, the gasifier design will allow for the
use of a single ram or multiple-finger ram.
[0117] In one embodiment, a multiple-finger ram is used when
minimum interference with gas flows is desirable during operation
of the rams.
[0118] In the multiple-finger ram designs, the multiple-finger ram
may be a unitary structure or a structure in which the ram fingers
are attached to a ram body, with individual ram fingers optionally
being of different widths depending on location. The gap between
the fingers in the multiple-finger ram design is selected to avoid
particles of reactant material from bridging.
[0119] In one embodiment, the individual fingers are about 2 to
about 3 inches wide, about 0.5 to about 1 inch thick with a gap
between about 0.5 to about 2 inches wide.
[0120] In one embodiment, the moving element is "T-shaped".
[0121] In certain embodiments in which the system operates at very
high temperatures, cooling can optionally be provided for the
moving elements. In one embodiment using a ram or shelf, cooling
within the ram or shelf can be provided. Such cooling could be by
fluid (for example, air or water) circulated inside the ram or
shelf from outside of the chamber.
[0122] In one embodiment, the plow has folding arms which can be
withdrawn when the plow is retracted.
[0123] In one embodiment, the conveyor is a belt or flighted chain
conveyor.
[0124] The moving element is constructed of material suitable for
use at high temperature. Such materials are well-known to those
skilled in the art and can include stainless steel, mild steel, or
mild steel partially protected with or fully protected with
refractory.
[0125] The guide elements can be located in the interior of the
gasifier or be internally mounted. Alternatively, the guide
elements can be located exterior to the gasifier or be externally
mounted.
[0126] In embodiments in which the guide elements are interior or
internal mounted, the lateral transfer system can be designed to
prevent jamming or debris entrapment.
[0127] In embodiments in which the guide elements are located
exterior to the gasifier or are externally mounted, the gasifier
includes at least one sealable opening through which the moving
element can enter the gasification chamber.
[0128] The guide element can include one or more guide channels
located in the side walls of the gasifier, guide tracks or rails,
guide trough or guide chains.
[0129] The guide engagement members can optionally include one or
more wheels or rollers sized to movably engage the guide element.
In one embodiment, the guide engagement member is a sliding member
comprising a shoe adapted to slide along the length of the guide
track. Optionally, the shoe further comprises at least one
replaceable wear pad.
[0130] In one embodiment, the lateral location of the moving
element is provided only at the point at which the moving element
enters the gasification chamber, with alignment elements ensuring
that the moving element is held angularly aligned at all times
thereby eliminating the need for complex, accurate guide
mechanisms.
[0131] In one embodiment, the alignment element is two chains
driven synchronously by a common shaft. The chains are optionally
individually adjustable to facilitate proper alignment.
[0132] In one embodiment, the lateral transfer system can be a
movable shelf/platform in which material is predominantly moved
through the gasifier by sitting on top of the shelf/platform. A
fraction of material may also be pushed by the leading edge of the
movable shelf/platform.
[0133] In one embodiment, the lateral transfer system can be a
carrier ram in which material is predominantly moved through the
gasifier by sitting on top of the carrier ram. A fraction of
material may also be pushed by the leading edge of the carrier
ram.
[0134] In one embodiment, the lateral transfer system can be a
pusher ram in which material is predominantly pushed through the
gasifier. Optionally, the ram height is substantially the same as
the depth of the material to be moved.
[0135] In one embodiment, the lateral transfer system can be a set
of conveyor screws. Optionally, the conveyor screws can be set in
the floor of the chamber thereby allowing material to be moved
without interfering with air introduction.
[0136] Power to propel the lateral transfer system is provided by a
motor and drive system and is controlled by actuators.
[0137] The individual lateral transfer units may optionally by
powered by dedicated motor and have individual actuators or one or
more lateral transfer units may be powered by a single motor and
shared actuators.
[0138] Basically any controllable motor or mechanical turning
device that can provide accurate control of the lateral transfer
system can be used to propel the lateral transfer system.
Appropriate motors and devices are known in the art and include
electric motors, motors run on syngas, steam, gases, gasoline,
diesel or micro turbines.
[0139] In one embodiment, the motor is an electric variable speed
motor which drives a motor output shaft selectably in the forward
or reverse directions. Optionally, a slip clutch could be provided
between the motor and the motor output shaft. The motor may further
comprise a gear box.
[0140] Movement of the lateral transfer system can be effected by a
hydraulic system, hydraulic rams, chain and sprocket drive, or a
rack and pinion drive. These methods of translating the motor
rotary motion into linear motion have the advantage that they can
be applied in a synchronized manner at each side of a unit to
assist in keeping the unit aligned and thus minimizing the
possibility of the mechanism jamming.
[0141] In one embodiment, the use of two chains per ram keep the
rams angularly aligned without the need for precision guides.
[0142] The externally mounted portions or components of the lateral
transfer unit is optionally housed in an unsealed, partially sealed
or sealed enclosure or casing. The enclosure may further comprise a
removable cover to allow for maintenance. In one embodiment, the
enclosure may have a higher internal pressure than the interior of
the gasification chamber; this may be achieved by the use of
nitrogen.
Chamber Heating System
[0143] The gasification process requires heat. Heat addition can
occur directly by partial oxidation of the feedstock or indirectly
by the use of one or more heat sources know in the art.
[0144] In one embodiment, the heat source can be circulating hot
air. The hot air can be supplied from, for example, air boxes, air
heaters or heat exchangers, all of which are known in the art.
[0145] In one embodiment, hot air is provided to each level by
independent air feed and distribution systems. Appropriate air feed
and distribution systems are known in the art and include separate
air boxes for each step level from which hot air can pass through
perforations in the floor of each step level to that step level or
via independently controlled spargers for each step level.
[0146] In one embodiment, each floor level has one or more grooves
running the length of individual steps. The grooves being sized to
accommodate hot air and/or steam pipes. The pipes optionally being
perforated on their lower third to half to facilitate the uniform
distribution of hot air or steam over the length of the step.
Alternatively, the sparger pipes can be perforated towards the top
of the pipes.
[0147] In one embodiment, the heat source can be circulating hot
sand.
[0148] In one embodiment, the heat source can be an electrical
heater or electrical heating elements.
[0149] In order to facilitate initial start up of the gasifier, the
gasifier can include access ports sized to accommodate various
conventional burners, for example natural gas, oil/gas or propane
burners, to pre-heat the chamber. Also, wood/biomass sources,
engine exhausts, electric heaters could be used to preheat the
chamber.
Process Additive Inputs
[0150] Process additives may optionally be added to the gasifier to
facilitate efficient conversion of feedstock into specified gases.
Steam input can be used to ensure sufficient free oxygen and
hydrogen to maximize the conversion of decomposed elements of the
input feedstock into product gas and/or non-hazardous compounds.
Air input can be used to assist in processing chemistry balancing
to maximize carbon conversion to a fuel gas (minimize free carbon)
and to maintain the optimum processing temperatures while
minimizing the cost of input heat.
[0151] Optionally, other additives may be used to optimize the
process and thereby improve emissions.
[0152] The invention, therefore, can include one or more process
additive inputs. These include inputs for steam injection and/or
air injection. The steam inputs can be strategically located to
direct steam into high temperature regions and into the product gas
mass just prior to its exit from the gasifier. The air inputs can
be strategically located in and around the gasifier chamber to
ensure full coverage of process additives into the processing
zone.
[0153] In one embodiment, the process additive inputs are located
proximal to the floor of the gasifier.
[0154] In one embodiment, the process additive inputs located
proximal to the floor are half-pipe air spargers trenched into the
refractory floor. Such air spargers may be designed to facilitate
replacement, servicing or modification while minimizing
interference with the lateral transfer of reactant material. The
number, diameter and placement of the air holes in the air spargers
can be varied according to system requirements or lateral transfer
system design.
[0155] In one embodiment, the process additive inputs are located
in the floor of the gasifier. Such process additive inputs are
designed to minimize plugging by fine particles or be equipped with
an attachment to prevent plugging. Optionally, the process additive
inputs can include a pattern of holes through which process
additives can be added. Various patterns of holes can be used
depending on system requirements or lateral transfer system design.
In choosing the pattern of the airholes, factors to consider
include avoiding high velocity which would fluidize the bed,
avoiding holes too close to gasifier walls and ends so that
channeling of air along refractory wall is avoided, and ensuring
spacing between holes was no more than approximately the nominal
feed particle size (2'') to ensure acceptable kinetics.
[0156] In one embodiment, airhole pattern is arranged such that
operation of the lateral transfer unit does interfere with the air
passing through the airholes.
[0157] In one embodiment in which a multiple-finger ram is used,
the pattern of the airholes is such that when heated the airholes
are between the fingers (in the gaps) and are in arrow pattern with
an offset to each other. Alternatively, the airhole pattern can
also be hybrid where some holes are not covered and others are
covered, such that even distribution of air is maximized (ie. areas
of floor with no air input at all are minimized).
[0158] In one embodiment, the pattern of holes facilitates the even
distribution of process additives over a large surface area with
minimal disruption or resistance to lateral material transfer.
[0159] In one embodiment, the process additive inputs provide
diffuse, low velocity input of additives.
[0160] In embodiments in which hot air is used to heat the chamber
additional air/oxygen injection inputs may optionally be
provided.
Service Ports
[0161] In one embodiment, the gasification chamber can further
comprise one or more ports. These ports can include service ports
(2020) to allow for entry into the chamber for maintenance and
repair. Such ports are known in the art and can include sealable
port holes of various sizes.
[0162] In one embodiment, access to the inside of the gasifier is
provided by a manhole at one end which can be closed by a sealable
refractory lined cover during operation.
[0163] In one embodiment, further access is available by removing
one or more air boxes.
[0164] The gasifier can optionally include a flanged lower section
which is connected to a flanged main section of the gasification
chamber to facilitate opening of the gasification chamber for
refractory inspection and repair.
Ash Removal System
[0165] The residual solids (ash) after gasification is complete can
optionally be removed from the gasifier and passed to a handling
system. The gasifier may therefore optionally include a
controllable solids removal system to facilitate solid residue or
ash removal.
[0166] In one embodiment, the controllable solids removal system
comprises a ram mechanism to push the ash out of the chamber.
[0167] In one embodiment, the controllable solids removal system
consists of a system of conveying rams. Optionally, the length of
the ram stroke can be controlled so that the amount of material fed
into a solid residue processing chamber with each stroke can be
controlled.
[0168] In a further embodiment of the invention, the controllable
solids removal system may comprise of a controllable rotating arm
mechanism.
[0169] As the material is processed and is moved from region to
region in the gasifier the heat generated within the pile can cause
melting which will result in agglomeration of the ash. Agglomerated
ash has been shown to cause jamming in drop port type exits. The
invention therefore can optionally comprise a means for breaking up
ash agglomerates.
[0170] In one embodiment, in order to ensure that any
agglomerations do not create jamming at the exit from the chamber,
a screw conveyor concept is used to extract the ash from the
gasifier. The ram motion will push the ash into the extractor and
the extractor will pull the ash out of the gasifier and feed it
into an ash conveyor system. Rotation of the extractor screw breaks
up agglomerations before the ash is fed into the conveyor system.
This breaking up action can be enhanced by having serrations on the
edge of the extractor screw flights.
Control
[0171] In one embodiment of the present invention, a control system
may be provided to control one or more processes implemented in,
and/or by, the various systems and/or subsystems disclosed herein,
and/or provide control of one or more process devices contemplated
herein for affecting such processes. In general, the control system
may operatively control various local and/or regional processes
related to a given system, subsystem or component thereof, and/or
related to one or more global processes implemented within a
system, such as a gasification system, within or in cooperation
with which the various embodiments of the present invention may be
operated, and thereby adjusts various control parameters thereof
adapted to affect these processes for a defined result. Various
sensing elements and response elements may therefore be distributed
throughout the controlled system(s), or in relation to one or more
components thereof, and used to acquire various process, reactant
and/or product characteristics, compare these characteristics to
suitable ranges of such characteristics conducive to achieving the
desired result, and respond by implementing changes in one or more
of the ongoing processes via one or more controllable process
devices.
[0172] The control system generally comprises, for example, one or
more sensing elements for sensing one or more characteristics
related to the system(s), processe(s) implemented therein, input(s)
provided therefor, and/or output(s) generated thereby. One or more
computing platforms are communicatively linked to these sensing
elements for accessing a characteristic value representative of the
sensed characteristic(s), and configured to compare the
characteristic value(s) with a predetermined range of such values
defined to characterise these characteristics as suitable for
selected operational and/or downstream results, and compute one or
more process control parameters conducive to maintaining the
characteristic value with this predetermined range. A plurality of
response elements may thus be operatively linked to one or more
process devices operable to affect the system, process, input
and/or output and thereby adjust the sensed characteristic, and
communicatively linked to the computing platform(s) for accessing
the computed process control parameter(s) and operating the process
device(s) in accordance therewith.
[0173] In one embodiment, the control system provides a feedback,
feedforward and/or predictive control of various systems,
processes, inputs and/or outputs related to the conversion of
carbonaceous feedstock into a gas, so to promote an efficiency of
one or more processes implemented in relation thereto. For
instance, various process characteristics may be evaluated and
controllably adjusted to influence these processes, which may
include, but are not limited to, the heating value and/or
composition of the feedstock, the characteristics of the product
gas (e.g. heating value, temperature, pressure, flow, composition,
carbon content, etc.), the degree of variation allowed for such
characteristics, and the cost of the inputs versus the value of the
outputs. Continuous and/or real-time adjustments to various control
parameters, which may include, but are not limited to, heat source
power, additive feed rate(s) (e.g. oxygen, oxidants, steam, etc.),
feedstock feed rate(s) (e.g. one or more distinct and/or mixed
feeds), gas and/or system pressure/flow regulators (e.g. blowers,
relief and/or control valves, flares, etc.), and the like, can be
executed in a manner whereby one or more process-related
characteristics are assessed and optimized according to design
and/or downstream specifications.
[0174] Alternatively, or in addition thereto, the control system
may be configured to monitor operation of the various components of
a given system for assuring proper operation, and optionally, for
ensuring that the process(es) implemented thereby are within
regulatory standards, when such standards apply.
[0175] In accordance with one embodiment, the control system may
further be used in monitoring and controlling the total energetic
impact of a given system. For instance, a given system may be
operated such that an energetic impact thereof is reduced, or again
minimized, for example, by optimising one or more of the processes
implemented thereby, or again by increasing the recuperation of
energy (e.g. waste heat) generated by these processes.
Alternatively, or in addition thereto, the control system may be
configured to adjust a composition and/or other characteristics
(e.g. temperature, pressure, flow, etc.) of a product gas generated
via the controlled process(es) such that such characteristics are
not only suitable for downstream use, but also substantially
optimised for efficient and/or optimal use. For example, in an
embodiment where the product gas is used for driving a gas engine
of a given type for the production of electricity, the
characteristics of the product gas may be adjusted such that these
characteristics are best matched to optimal input characteristics
for such engines.
[0176] In one embodiment, the control system may be configured to
adjust a given process such that limitations or performance
guidelines with regards to reactant and/or product residence times
in various components, or with respect to various processes of the
overall process are met and/or optimised for. For example, an
upstream process rate may be controlled so to substantially match
one or more subsequent downstream processes.
[0177] In addition, the control system may, in various embodiments,
be adapted for the sequential and/or simultaneous control of
various aspects of a given process in a continuous and/or real time
manner.
[0178] In general, the control system may comprise any type of
control system architecture suitable for the application at hand.
For example, the control system may comprise a substantially
centralized control system, a distributed control system, or a
combination thereof. A centralized control system will generally
comprise a central controller configured to communicate with
various local and/or remote sensing devices and response elements
configured to respectively sense various characteristics relevant
to the controlled process, and respond thereto via one or more
controllable process devices adapted to directly or indirectly
affect the controlled process. Using a centralized architecture,
most computations are implemented centrally via a centralized
processor or processors, such that most of the necessary hardware
and/or software for implementing control of the process is located
in a same location.
[0179] A distributed control system will generally comprise two or
more distributed controllers which may each communicate with
respective sensing and response elements for monitoring local
and/or regional characteristics, and respond thereto via local
and/or regional process devices configured to affect a local
process or sub-process. Communication may also take place between
distributed controllers via various network configurations, wherein
a characteristics sensed via a first controller may be communicated
to a second controller for response thereat, wherein such distal
response may have an impact on the characteristic sensed at the
first location. For example, a characteristic of a downstream
product gas may be sensed by a downstream monitoring device, and
adjusted by adjusting a control parameter associated with the
converter that is controlled by an upstream controller. In a
distributed architecture, control hardware and/or software is also
distributed between controllers, wherein a same but modularly
configured control scheme may be implemented on each controller, or
various cooperative modular control schemes may be implemented on
respective controllers.
[0180] Alternatively, the control system may be subdivided into
separate yet communicatively linked local, regional and/or global
control subsystems. Such an architecture could allow a given
process, or series of interrelated processes to take place and be
controlled locally with minimal interaction with other local
control subsystems. A global master control system could then
communicate with each respective local control subsystems to direct
necessary adjustments to local processes for a global result.
[0181] The control system of the present invention may use any of
the above architectures, or any other architecture commonly known
in the art, which are considered to be within the general scope and
nature of the present disclosure. For instance, processes
controlled and implemented within the context of the present
invention may be controlled in a dedicated local environment, with
optional external communication to any central and/or remote
control system used for related upstream or downstream processes,
when applicable.
[0182] Alternatively, the control system may comprise a
sub-component of a regional an/or global control system designed to
cooperatively control a regional and/or global process. For
instance, a modular control system may be designed such that
control modules interactively control various sub-components of a
system, while providing for inter-modular communications as needed
for regional and/or global control.
[0183] The control system generally comprises one or more central,
networked and/or distributed processors, one or more inputs for
receiving current sensed characteristics from the various sensing
elements, and one or more outputs for communicating new or updated
control parameters to the various response elements. The one or
more computing platforms of the control system may also comprise
one or more local and/or remote computer readable media (e.g. ROM,
RAM, removable media, local and/or network access media, etc.) for
storing therein various predetermined and/or readjusted control
parameters, set or preferred system and process characteristic
operating ranges, system monitoring and control software,
operational data, and the like. Optionally, the computing platforms
may also have access, either directly or via various data storage
devices, to process simulation data and/or system parameter
optimization and modeling means. Also, the computing platforms may
be equipped with one or more optional graphical user interfaces and
input peripherals for providing managerial access to the control
system (system upgrades, maintenance, modification, adaptation to
new system modules and/or equipment, etc.), as well as various
optional output peripherals for communicating data and information
with external sources (e.g. modem, network connection, printer,
etc.).
[0184] The processing system and any one of the sub-processing
systems can comprise exclusively hardware or any combination of
hardware and software. Any of the sub-processing systems can
comprise any combination of none or more proportional (P), integral
(I) or differential (D) controllers, for example, a P-controller,
an I-controller, a PI-controller, a PD controller, a PID controller
etc. It will be apparent to a person skilled in the art that the
ideal choice of combinations of P, I, and D controllers depends on
the dynamics and delay time of the part of the reaction process of
the gasification system and the range of operating conditions that
the combination is intended to control, and the dynamics and delay
time of the combination controller. It will be apparent to a person
skilled in the art that these combinations can be implemented in an
analog hardwired form which can continuously monitor, via sensing
elements, the value of a characteristic and compare it with a
specified value to influence a respective control element to make
an adequate adjustment, via response elements, to reduce the
difference between the observed and the specified value. It will
further be apparent to a person skilled in the art that the
combinations can be implemented in a mixed digital hardware
software environment. Relevant effects of the additionally
discretionary sampling, data acquisition, and digital processing
are well known to a person skilled in the art. P, I, D combination
control can be implemented in feed forward and feedback control
schemes.
[0185] In corrective, or feedback, control the value of a control
parameter or control variable, monitored via an appropriate sensing
element, is compared to a specified value or range. A control
signal is determined based on the deviation between the two values
and provided to a control element in order to reduce the deviation.
It will be appreciated that a conventional feedback or responsive
control system may further be adapted to comprise an adaptive
and/or predictive component, wherein response to a given condition
may be tailored in accordance with modeled and/or previously
monitored reactions to provide a reactive response to a sensed
characteristic while limiting potential overshoots in compensatory
action. For instance, acquired and/or historical data provided for
a given system configuration may be used cooperatively to adjust a
response to a system and/or process characteristic being sensed to
be within a given range from an optimal value for which previous
responses have been monitored and adjusted to provide a desired
result. Such adaptive and/or predictive control schemes are well
known in the art, and as such, are not considered to depart from
the general scope and nature of the present disclosure.
Control Elements
[0186] Sensing elements contemplated within the present context, as
defined and described above, can include, but are not limited to,
temperature sensing elements, position sensors, proximity sensors,
pile height sensors and means for monitoring gas.
[0187] In one embodiment, the gasifier further comprises a
temperature sensor array comprising one or more removable
thermocouples. The thermocouples can be strategically placed to
monitor temperature at points along each stage and at various
heights at each stage.
[0188] Appropriate thermocouples are known in the art and include
bare wire thermocouples, surface probes, thermocouple probes
including grounded thermocouples, ungrounded thermocouples and
exposed thermocouples or combinations thereof.
[0189] In one embodiment, individual thermocouples are inserted
into the chamber via a sealed end tube (thermowell) which is then
sealed to the vessel shell, allowing for the use of flexible wire
thermocouples which are procured to be longer than the sealing tube
so that the junction (the temperature sensing point) of the
thermocouple is pressed against the end of the sealed tube to
assure accurate and quick response to temperature change (see FIG.
28).
[0190] Optionally, to prevent material from getting blocked by the
thermocouple tube the end of the sealed tube cap can be fitted with
a deflector. In one embodiment, the deflector is a square flat
plate, with bent corners that contact the refractory and are
in-line with reactant material flow to slip-stream particles over
the thermowell (see FIG. 28).
[0191] In addition, the invention may comprise devices for
monitoring the exit of gas. In one embodiment this can include a
gas composition monitor and gas flow meter.
[0192] By measuring process temperatures throughout the material
pile, gas phase temperatures above the pile, and by measuring
resultant off-gas flowrate and analyzing off-gas composition, the
amount of air injected can be optimized to maximize efficiency and
minimize undesirable process characteristics and products including
slagging of ash, combustion, poor off-gas heating value, excessive
particulate matter and dioxin/furan formation thereby meeting or
bettering local emission standards. Such measurements can be taken
during initial start-up or initially testing of the gasifier,
periodically or continually during operation of the gasifier and
may optionally be taken in real time.
[0193] In one embodiment, the gasifier can optionally comprise a
pressure sensor or monitor within the gasifier.
[0194] The gasifier can further comprise level switches or monitors
to assess pile height. Appropriate level switches, sensors and
monitors are known in the art. In one embodiment, the level
instrumentation comprises point-source level switches.
[0195] In one embodiment, the level switches are microwave devices
with an emitter on one side of the chamber and a receiver on the
other side, which detects either presence or absence of solid
material at that point inside the gasification chamber.
[0196] A worker skilled in the art would readily be able to
determine the appropriate placement of level switches, sensors and
monitors such that the desired reactant material pile profile can
be obtained.
[0197] In one embodiment, the gasifier further comprises proximity
or position sensors.
[0198] Response elements contemplated within the present context,
as defined and described above, can include, but are not limited
to, various control elements operatively coupled to process-related
devices configured to affect a given process by adjustment of a
given control parameter related thereto. For instance, process
devices operable within the present context via one or more
response elements, may include, but are not limited to elements
controlling chamber heating, elements controlling process additives
and elements controlling lateral transfer system movement.
Control System for the Lateral Transfer System
[0199] A level control system is required to maintain stable pile
height inside the gasifier. Stable level control prevents
fluidization of the reactant material from process air injection
which could occur at low level and to prevent poor temperature
distribution through the pile owing to restricted airflow that
would occur at high level. Maintaining stable level also maintains
consistent gasifier residence time by keeping the volume of
reacting material constant.
[0200] Optionally, a series of level switches in the gasifier
measure pile depth. The level switches are optionally microwave
devices with a emitter on one side of the chamber and a receiver on
the other side, which detects either presence or absence of solid
material at that point inside the gasifier.
[0201] The lateral transfer units move as necessary to ensure that
pile height is controlled at the desired level. To accomplish this
in embodiments in which the lateral transfer units comprise rams,
the rams move in a series of programmed step of which there are
several key control parameters including: specific ram movement
sequence, ram speed, ram distance, and ram sequence frequency.
[0202] In general, rams move out to a set point distance, or until
a controlling level switch is tripped; either at the same time or
in a pre-determined sequence. The level switch control action can
be based on a single switch, tripping either empty or full, or may
require multiple switches tripping, empty or full, or any
combination thereof. Afterwards, the rams move back to end the
cycle, and the process is repeated. There is an optional delay
between cycles as required by the process and residence time
requirements of the gasifier.
[0203] To ensure efficient movement of material in the
stepped-floor embodiments, the sequencing of lateral transfer unit
movement can be optimized by starting at the lowest level of the
gasifier, creating a pocket, then filling it from the step above
before the lateral transfer unit's moving element is retracted to
prevent pull back of the pile and then repeating up the steps.
[0204] In one embodiment, the ram sequencing comprises the lowest
ram is extended first; the middle ram is then extended which pushes
material down onto the lowest ram filling the void created by that
rams movement; the lowest ram is then retracted; the upper ram is
then extended filling the void at the back of the middle ram; the
middle ram is then retracted; new material dropping from the feed
port fills any void on the top ram and the top ram is retracted.
Optionally, all of these motions can be controlled automatically
and independently by the control system in response to system
instrumentation data.
[0205] In one three-step embodiment, the gasifier throughput is set
by adjusting the volumetric feed rate into the gasifier. The level
control system then controls the lateral transfer unit's moving
elements as needed to control level of the pile on each step on
aim, which includes controlling the rate of ash discharge from the
gasifier.
[0206] In one three-step embodiment, the Step C lateral transfer
unit's moving element sets gasifier throughput by moving a fixed
length in relation to location indicator or guide point and
frequency to discharge ash from the gasifier. The Step B lateral
transfer unit's moving element follows and moves as far as
necessary to translocate material onto Step C and change the Step C
start-of-stage level switch state to "full". The Step A lateral
transfer unit's moving element follows and moves as far as
necessary to push material onto Step B and change the Step B
start-of-stage level switch state to "full". All lateral transfer
units' moving elements are then withdrawn simultaneously, and a
scheduled delay can be executed before the entire sequence is
repeated. Additional configuration may be used to limit the change
in consecutive stroke lengths to less than that called for by the
level switches to avoid excess lateral transfer unit-induced
disturbances.
[0207] Optionally, full extension of the lateral transfer unit's
moving element to the end of each step may need to be programmed to
occur occasionally to prevent stagnant material from building up
and agglomerating near the end of the step.
Temperature Control
[0208] In order to get the best possible conversion efficiency, the
temperatures in the gasifier and temperature distribution through
the pile can be stabilized and controlled.
[0209] Temperature control within the pile can be achieved by
changing the flow of process air into a given region or step. The
process air flow provided to each step in the bottom chamber can be
adjusted to stabilize temperatures in each step. Optionally,
temperature control utilizing extra lateral transfer unit's moving
element may also be necessary to break up hot spots and to avoid
bridging.
[0210] In one embodiment, temperature control within the pile is
achieved by changing the flow of process air into a given step (ie.
more or less combustion). For example, the process air flow
provided to each step in the gasifier may be adjusted by the
control system to stabilize temperatures at step. Temperature
control utilizing extra ram strokes may also be used to break up
hot spots and to avoid bridging.
[0211] In one embodiment, the air flow at each step is pre-set to
maintain substantially constant temperature ranges and ratios
between steps. For example, about 36% of the total air flow may be
directed to Step A, about 18% to Step B, and about 6% to Step C,
the remainder being directed to an attached gas reformulating
chamber (e.g. 40% of total air flow). Alternatively, air input
ratios may be varied dynamically to adjust temperatures and
processes occurring within each step of the gasifier and/or
reformer.
Downstream Options
[0212] The gasifier of the invention can be adapted for a variety
of applications including waste disposal and syngas production. The
gasifier can therefore be a component of a larger system depending
on the application.
[0213] In one embodiment, the gasifier is adapted for waste
disposal applications and is in gaseous communication with a flare
stack fitted with appropriate pollution abatement devices.
[0214] In one embodiment, the gasifier is a component of a syngas
generating system and comprises a cyclonic oxidizer, a gas
refinement system or a gas reformulating system.
[0215] In one embodiment, the gasifier is a component of a
hazardous treatment facility.
[0216] Cyclonic oxidizer, a gas refinement system or a gas
reformulating system utilize a plasma heat source to refine the
off-gas.
EXAMPLES
Example 1
[0217] Referring to FIGS. 4 to 10, in one embodiment, the gasifier
(2100) comprises a refractory-lined horizontally-oriented
gasification chamber (2102) having a feedstock input (2104), gas
outlet (2106), a solid residue outlet (2108), and various service
(2120) and access ports (2122). The gasification chamber (2102) has
a stepped floor with a plurality of floor levels (2112, 2114 and
2116). Each floor level is sloped between about 5 and about 10
degrees. Each floor level has a series of additive inputs (2126)
located in the side walls proximal to the floor level to allow for
the addition of oxygen and/or steam.
[0218] Movement through the steps is facilitated by the lateral
transfer system. In this example, FIGS. 4 to 9, the lateral
transfer system comprises a series of moving shelf units (2128,
2130, 2132) in which material is predominantly moved through the
gasifier by sitting on top of the shelf with a small fraction of
material being pushed by the leading edge of the shelf. As shown,
each floor level is serviced by a moving shelf unit (2128, 2130,
2132) mounted on an external frame (2134). Corresponding sealable
openings in the gasification chamber walls allow for entry of each
moving shelf. Thus the moving shelf units (2128, 2130, 2132) are
capable of moving material along floor levels (2112, 2114, 2116)
respectively at a controlled rate. The distance individual shelves
travel across their respective step is controlled by an externally
mounted controller. The ability to control the start and the stop
point for each push allows for control of pile height through the
gasification chamber. In normal operation, after material has been
moved as required, the shelf may be fully or partially withdrawn
from the chamber; for example, the shelf may be withdrawn just out
of the processing region but still inside the refractory, to permit
processing gas to be introduced from the bed of the chamber. This
is particularly applicable to the final processing zone where the
material is more dust-like and needs to be fluidized by multiple
gas introduction points from the floor of the chamber. Withdrawal
of the shelf also avoids unnecessary heating of the shelf and loss
of heat from the process.
[0219] The externally mounted controller is a gearhead synchronous
motor (2156) coupled to the moving shelf by means of roller chains
(2166). Start and stop points for moving shelf motion is remotely
controlled by a process computer. Speed and frequency of motion is
also controlled by the computer.
[0220] Referring now to FIGS. 8, 9 and 10, each moving shelf unit
comprises an externally mounted guide portion (2136), moving
element or shelf (2138) having guide portion engagement members,
externally mounted drive system and an externally mounted
controller. The externally mounted portions of the moving shelf
units is housed in a sealed enclosure (2139). The enclosure further
comprises a removable cover to allow for maintenance.
[0221] Referring to FIGS. 8 and 9, the guide portion comprises a
pair of generally parallel elongated tracks (2140(a), 2140(b))
mounted on the frame (shown in part) (2134). The angle of the
individual tracks corresponding in general to the slope of the
corresponding step. Each of the tracks has a substantially
rectangular cross-section. The moving element comprises an
elongated rectangular block (2144) sized to slidably move through
the corresponding sealable opening in the chamber wall.
[0222] Referring to FIG. 10, the leading edge of the elongated
rectangular block is substantially perpendicular to the floor of
the gasification chamber. The leading lower edge of the elongated
rectangular block that contacts the refractory (2146) of the
chamber is sharp to reduce the risk of riding up on top of the
material and jamming the mechanism. The sharp leading edge is
designed to be effectively self-sharpening. As it is sliding flat
against the refractory floor there will be a slight wearing of the
bottom surface of the shelf (2128), thus tending to sharpen the
forward edge. The shelf is designed to be easily removable for
maintenance that could include replacement of the endpiece or
grinding of the fixed end.
[0223] The elongated rectangular block is adapted to sealingly
engage the chamber wall and has substantially smooth parallel faces
such that it is possible to obtain sealing against each face to
prevent material egress and air ingress during normal process
operation, and also to control hazardous gas escape during abnormal
situations. The seal is located at the inside face of the
refractory and is resiliently held against the sliding faces of the
shelves. This minimizes material escape and gas leakage and
precludes the likelihood of jamming of a shelf. The seals (2148)
are designed to be easily replaceable during operation and are
manufactured from stainless steel.
[0224] As shown in FIG. 10, the moving shelf further comprise a
scraper (2150) to remove material from the shelf as it is withdrawn
(or partially withdrawn) from the chamber. The scraper is a
one-piece sheet metal part fixed to outside frame and is designed
to be readily replaceable during operation.
[0225] The elongated rectangular block (2144) is mounted on
substantially parallel brackets. Each bracket having at least two
guide engagement members (2154). The guide engagement members
illustrated in FIG. 8 are rollers sized to movably engage the track
(2140(a) or 2140(b)).
[0226] Power to propel the elongated rectangular block along the
tracks is supplied by a externally mounted electric variable speed
motor (2156) which drives a motor output shaft (2158) selectably in
the forward or reverse direction allowing for extension and
retraction of the elongated rectangular block at a controlled rate.
A slip clutch is provided between the motor (2156) and the motor
output shaft (2158). The motor further comprise a gear box. Two
driver sprocket gears (2160) are mounted on the motor output shaft.
The driver sprockets (2160) and corresponding driven sprockets
(2162) mounted on an axle (2164) operatively mesh with chain
members (2166) which are secured by brackets (2168) to the
elongated rectangular block (2144).
[0227] The ram stroke is controlled by proximity and limit switches
so that the amount of material fed into the chamber with each
stroke is controlled. A switch is also used to verify the start
position of the rams and length and speed is then controlled by a
variable frequency drive in the motor controller.
Example 2
[0228] Referring to FIGS. 11 to 25, in one embodiment the gasifier
(2200) comprises a refractory-lined horizontally-oriented
gasification chamber (2202) having a feedstock input (2204), gas
outlet (2206), a solid residue outlet (2208), and various service
(2220) and access ports (2222). The gasification chamber (2202) is
a refractory-lined steel weldment having a stepped floor with a
plurality of floor levels (2212, 2214 and 2216).
[0229] The solid residue outlet is equipped with an ash extractor
comprising an extractor screw (2209) which will pull the ash out of
the gasifier and feed it into an ash conveyor system.
[0230] Referring to FIG. 16, the refractory is a multilayer design
with a high density chromia layer (2402) on the inside to resist
the high temperature, abrasion, erosion and corrosion, a middle,
high density alumina layer with medium temperature resistance and
insulation factor (2404) and an outer very low density insboard
material with very high insulation factor (2406) that can be used
because it will not be exposed to abrasion of erosion. The
refractory lines the metal shell (2408) of the gasification
chamber.
[0231] Each level or step has a perforated floor (2270) through
which heated air is introduced. To avoid blockage of the air holes
during processing, the air hole size is selected such that it
creates a restriction and thus a pressure drop across each hole.
This pressure drop is sufficient to prevent waste particles from
entering the holes. The holes are tapered outwards towards the
upper face to preclude particles becoming stuck in a hole. In
addition, the movement of the lateral transfer units may dislodge
any material blocking the holes.
[0232] The air feed for each level or step is independently
controllable. Independent air feed and distribution through the
perforated floors (2270A, 2270B, 2270C) of each step is achieved by
a separate air box (2272, 2274, and 2276) which forms the floor at
each step.
[0233] Referring to FIGS. 17 and 18, to reduce the risk of
stress-related failure or buckling of the air box, several features
are included. The material for the perforated top plate (2302) of
the air boxes is an alloy that meets the corrosion resistance
requirements for the system. The perforated top sheet (2302) is
relatively thin, with stiffening ribs and structural support
members (2304) to prevent bending or buckling.
[0234] To minimize stress on the flat front, top and bottom sheets
of the boxes, perforated webs is attached between both sheets. To
allow for thermal expansion in the boxes they are attached only at
one edge and are free to expand at the other three edges.
[0235] Referring to FIGS. 17, the fixed edge of the Step A & B
boxes (2272 and 2274) is also the connection point of the input air
piping (2278) thus, the connection flange (2280) will be at high
temperature and must be sealed to the cool wall of the gasifier. A
shroud concept is used. The hot air box (2272) and pipe (2278) are
attached to one end of the shroud and the other end of the shroud
(2282) is connected to the cool gasifier (2200). A temperature
gradient will occur across the length of the shroud (2282), thus
there will be little or no stress at either connection. The space
between the shroud (2282) and the internal duct of the air box
(2272) is filled with insulation to retain heat and to ensure the
temperature gradient occurs across the shroud. When the air box
2270A, (2272) is in its operating location in the chamber the top
plate opposite to the air connection is extended beyond the air box
to rest on a shelf of refractory. This provides support to the air
box when operating and also acts as a seal to prevent material from
falling below the air box. At the same time it allows free movement
to allow for expansion of the air box.
[0236] Referring to FIG. 21, the downstream edge of the air box can
be dealt with in the same way. The upstream edge of the air box is
sealed with a resilient sheet sealing (2306) between the ram and
the air box top plate (2302).
[0237] Connection to the hot air supply piping is via a horizontal
flange such that to enable removal of an air box requires only the
flange to be disconnected to permit the removal to take place.
[0238] The third step air box (2276) is inserted from below and
uses the shroud concept for sealing and locating the box to the
gasifier (2200). The general arrangement of the third step air box
is shown in FIG. 19.
[0239] Sealing against dust falling around the edges of the third
stage box is achieved by having it set underneath a refractory
ledge at the edge of the second stage. The sides can be sealed by
flexible seals protruding from below recesses in the sides of the
refractory. These seals sit on the top face of the box, sealing
between the walls and the box. The downstream edge of the air box
is dust sealed to the side of an extractor trough using a flexible
seal.
[0240] To permit removal of the third stage air box, the hot air
pipe connection is vertical.
[0241] Movement through the steps is facilitated by lateral
transfer system. Referring to FIGS. 24 to 25, in this Example, the
lateral transfer system comprises a series of multiple-finger
carrier rams (2228, 2230, 2232), with a single multiple-finger
carrier ram servicing each step. The system of carrier rams further
allows for the control of the height of the pile at each step and
the total residence time in the chamber. Each carrier ram is
capable of movement over the full or partial length of that step,
at variable speeds.
[0242] Referring to FIG. 24, each carrier ram unit comprises an
externally mounted guide portion, a multiple-finger carrier ram,
externally mounted drive system and an externally mounted
controller.
[0243] The multiple-finger carrier ram is a structure in which
fingers (2328) are attached to a ram body (2326), with individual
fingers being of different widths depending on location. The gap
between the fingers in the multiple-finger carrier design is
selected to avoid particles of reactant material from bridging. The
individual fingers are about 2 to about 3 inches wide, about 0.5 to
about 1 inch thick with a gap between about 0.5 to about 2 inches
wide.
[0244] The air box airhole pattern is arranged such that operation
of the rams does interfere with the air passing through the
airholes.
[0245] The multiple-finger carrier ram has independent flexibility
built-in so that the tip of each finger (2328) can more closely
comply with any undulations in the air box top face. This
compliance has been provided by attaching the fingers (2328) to the
ram body (2326) using shoulder bolts, which do not tighten on the
finger. This concept also permits easy replacement of a finger.
[0246] The end of the ram finger is bent down to ensure that the
tip contacts the top of the air in the event that the relative
locations of the ram and airbox change due, for example, to
expansions. This feature also lessens any detrimental effect on the
process due to air holes being covered by the ram, the air will
continue to flow through the gap between the ram and air box.
[0247] Referring to FIGS. 24 and 25, the guide portion comprises a
pair of generally horizontal, generally parallel elongated tracks
(2240(a), 2240(b)) (not shown) mounted on a frame. Each of the
tracks has a substantially L-shaped cross-section. The moving
element comprises a ram body (2326) and a series of elongated,
substantially rectangular ram fingers (2328) sized to slidably move
through corresponding sealable opening in the chamber wall. The ram
fingers are constructed of material suitable for use at high
temperature.
[0248] The ram fingers are adapted to sealingly engage the chamber
wall to avoid uncontrolled air from entering the gasifier, which
would interfere with the process or could create an explosive
atmosphere. It is also necessary to avoid escape of hazardous toxic
and flammable gas from the chamber, also, excessive debris escape
is undesirable. Gas escape to atmosphere is prevented by containing
the ram mechanisms in a sealed box. This box comprises a nitrogen
purge facility to prevent formation of an explosive gas mixture
within the box. Debris sealing and limited gas sealing is provided
for each finger of the ram. The sealing is in the form of a
flexible strip (2308) pressing against each surface of each finger
of the rams, see FIG. 22.
[0249] Leakage of debris is monitored by means of windows in the
sealed box and a dust removal facility is provided to facilitate
the removal of debris. This removal can be accomplished without
breaking the seal integrity of the ram box, see FIG. 23.
[0250] The dust removal facility (2310) comprises a metal tray
(2312) having a dust outlet (2314) equipped with a shutter (2316)
and attachment site (2318) for a dust can (2332), and a
manual-operated, chain (2320) driven dust pusher (2322). Dust is
pushed to the outlet (2314) by the pusher (2322) when the operator
handle (2324) is used.
[0251] Power for moving the rams is provided by electric motors
which drive the ram via a gearbox and roller chain system (as
described in Example 1). Briefly, power to propel the rams along
the tracks is supplied by a externally mounted electric variable
speed motor (2256) which drives a motor output shaft (2258)
selectably in the forward or reverse direction allowing for
extension and retraction of the ram at a controlled rate. A
position sensors (2269) transmit ram position information to the
control system. Two driver sprocket gears (2260) are mounted on the
motor output shaft. The driver sprockets (2260) and corresponding
driven sprockets (2262) mounted on an axle (2264) operatively mesh
with chain members (2266) which are secured by brackets (2268) to
the elongated rectangular block (2244).
[0252] The motors are controlled by the overall control system
which can command start and stop position, speed of movement and
frequency of movement. Each ram is controlled independently. There
is a tendency for the material on top of the ram to be pulled back
when the ram is withdrawn. This tendency is dealt with by
appropriately sequencing the ram strokes.
Example 3
[0253] Referring to FIG. 26, in the embodiment of the invention
described in Example 2 a staggered ram sequence control strategy
can be implemented to facilitate movement of the rams. A summary of
an exemplary ram sequence is as follows: [0254] 1. Ram C (2232)
move fixed distance (with adjustable setpoint), creating a pocket
at the start of Step C (2216). [0255] 2. Ram B (2230) follows as
soon as Ram C (2232) passes a trigger distance (trigger distance
has adjustable setpoint). Ram B pushes/carries material to
immediately fill the pocket at the start of Step C (2216). Feedback
control is to stroke as far as necessary to block level switch C
(2217), or minimum setpoint distance if already blocked, or maximum
setpoint distance if blocking does not occur. At the same time as
Ram B (2230) is filling the pocket at the start of Step C (2216),
it is creating a pocket at the start of Step B (2230). [0256] 3.
Ram A (2228) follows as soon as Ram B (2228) passes a trigger
distance. Ram A (2228) pushes/carries material to immediately fill
the pocket at the start of Step B (2214). Feedback control is to
stroke as far necessary to block level switch B (2215), or minimum
setpoint distance if already blocked, or maximum setpoint distance
if blocking does not occur. At the same time as Ram A (2228) is
filling the pocket at the start of Step B (2214), it is also
creating a pocket at the start of Step A (2212). This typically
triggers the feeder to run and fill the gasifier until level switch
A (2213) is blocked again. [0257] 4. All rams reverse to home
position simultaneously.
[0258] The reactant material profile obtained by such a sequencing
strategy is show in FIG. 27 (Profile B).
* * * * *